The present invention relates to an apparatus and method for scanning a substrate, namely photographic film or the like, whether scanning onto a substrate for image recording or scanning an image off of a substrate, i.e. input scanning. More particularly, the invention relates to a scanning lens which rotates on an axis normal to the scan plane. While the invention is described primarily as an image scanning lens for producing an image on a substrate, the invention can be employed in an input scanning device as well.
As used herein, the term "film" is intended to mean any type of image recording medium, including photographic film, thermal media, dye transfer media, photo-electro-static (xerographic) transfer surfaces, and the like, and is not to be construed only as photographic film.
Many imaging tasks such as recording an image onto film one pixel at a time or scanning an image off of film one pixel at a time require the ability to rapidly and accurately move the film and the imaging optics in relation to one another in a path that covers the area of the image. Conventional raster scan methods use straight lines of samples called scanlines spaced uniformly along a second axis. This is convenient for many devices such as CRT's and certainly is convenient for software and digital electronics where memory and coordinate systems are organized into rows and columns.
In a conventional film recorder, a light beam from a cathode ray tube ("CRT") or the like is controlled by a deflection system to scan across a stationary frame of photographic film to expose the film with an image. Typically, the images are generated by a computer for the production of slides, transparencies, photographs or the like. Alternatively, the images can comprise natural images acquired by a scanner or television camera for subsequent processing by a computer.
Known film recorders, such as those sold under the trademark SOLITAIRE.RTM. by Management Graphics, Inc. of Minneapolis, Minn., U.S.A., typically include a light source such as a CRT for producing a beam, a deflection system for scanning the beam across the face of the CRT, a system control and central processor unit ("CPU") for controlling the deflection system, and a camera (i.e., "film transport"). The later component may include a film transport body, lens, lens mounting assembly, aperture plate, film plate, and film transport mechanism. One type of film transport mechanism that is widely in use is a shuttle style film gate. Such transports are manufactured, for example, by Oxberry Corporation of Mamaroneck, N.Y., U.S.A.
On a Solitaire.RTM. film recorder, an image to be recorded is first written on the phosphor of the CRT by deflecting an electron beam in a raster pattern and modulating the intensity of the beam. This process is analogous to the creation of a television picture. Alternatively, the image can be written on the CRT using well known time modulation techniques, wherein the beam intensity is constant but the time the beam is kept at each point is varied depending on the exposure required.
The resulting pattern (the "object image") on the CRT is optically imaged onto photographic film by the film transport, which contains the required optics and mechanism to advance the film to successive frames. Other types of light sources can be substituted for the CRT in a film recorder. Examples include fiber optic sources, lasers and focused light impinging on the film or other substrate mounted on a rotating drum wherein one or more rotations are completed for each scan line.
When it comes to mechanically creating a repetitive motion that scans an image in a raster fashion, difficulties arise. Many systems have been designed in the past that utilize the advantages of circular or pivoting motions to accomplish the scanning task, but in order to maintain the row/column raster organization of the image data, additional complications such as holding the film in a curved shape or adding a field-flattening or f-theta lens to the system are introduced.
It would be very advantageous to provide a system that could utilize a circular scanning motion in the fastest scanning direction and yet maintain the simplicity of a flat image plane.
The present invention provides a scanning lens which rotates around an axis normal to the flat scan plane of the substrate to be scanned having the aforementioned and other advantages.